Cylindrical light diffusing device for use in photoimmunotherapy

ABSTRACT

The present invention provides a cylindrical light diffusing device comprising a non-circular core fiber having (i) a fiber core that provides a “top hat” core irradiance distribution; (ii) light blocking means that prevent frontal light emisson from distal end of the non-circular core fiber; and (iii) a light diffusing section having a diffusing proximal end, a diffusing distal end, and internal scattering features distributed within the fiber core of the light diffusing section along central axis of the fiber core, wherein the light diffusion section emits irradiance in a radially symmetric longitudinally “top hat” diffusing irradiance distribution.

CLAIM OF BENEFIT OF FILING DATE

This application claims the benefit of the filing date of U.S.Provisional Application Ser. No. 62/412,606 titled: “Light DiffusingDevice for Use in Photoimmunotherapy” filed on Oct. 25, 2016 and U.S.Provisional Application Ser. No. 62/529,507 titled: “Frontal LightDiffusing Device for Use in Photoimmunotherapy” filed on Jul. 7, 2017,which are incorporated herein by reference for all purposes.

FIELD OF INVENTION

The present invention relates to a medical device for performingphotoimmunotherapy (“PIT”), photodynamic therapy (“PDT”) or other lightactivated treatments upon tissue of an organism, cellular or acellularorganisms and methods of using such medical device in PIT, PDT or otherlight activated therapies. More particularly, the invention is a fiberoptic diffuser device to deliver light in a desired illumination patternand wavelength for PIT, PDT or other light therapies to an area undertreatment.

BACKGROUND OF THE INVENTION

PIT, PDT and other light activated therapies have been used to treatvarious maladies and diseases. PIT and PDT and other light activatedtherapies often involve the use of an exogenous or endogenousphotosensitizing agent or substance that is activated by electromagneticradiation (e.g., light such as laser light, LED light, etc.). PIT isbased on a new drug system that consists of a cancer targetingmonoclonal antibody conjugated to a photoactivatable molecule. Thetargeting agent can include other moieties such as ligands, viralcapsid, peptides, liposomes, nanoparticles, etc. This drug conjugate isnot pharmacologically active until the conjugate is bound to the cancercells and gains anticancer activity upon light-mediated activation atthe tumor site. Tumor targeting and context precision activation of thedrug provides exquisite cancer specificity and permits rapid cancer cellkilling without damage to the surrounding healthy tissues. Anticanceractivity of PIT is highly effective and it works with multiple types ofmonoclonal antibodies and other targeting moieties, thus the platformenables the targeting of a broad range of cancer antigens and tumortypes. It should be noted that the present invention is not limited totargeting tumor sites. Instead, the present invention can also be usedto target other cellular and acellular organisms including bacteria,fungi, viruses, prions, etc. in order to treat or prevent disease(s).

The basic requirements for PIT and/or PDT light sources are to match theactivation spectrum of the exogenous or endogenous photosensitizer(usually the wavelength of peak absorbance) and to generate adequatepower at this wavelength, deliverable to the target tissue ergonomicallyand with high efficiency. Typically, 1-5 W of usable power are requiredin the 630-850 nm range at irradiances of up to several hundred mW cm⁻²in order to deliver treatments in tens of minutes. In addition, thesources must be reliable in the clinical environment and becost-effective.

For illumination of the area to be treated (“treatment area”), usuallycylindrical and frontal (superficial) diffusers, sometimes also called“micro lens diffusers”, are generally used. The fiber optic cylindrical(side firing) and superficial (front firing) diffusers consist ofmultimode fiber assemblies with a round core/cladding structure from50-1000 um core diameter with attached diffusing section that can beconnected directly to a light source, for instance by means of anoptical connector.

I. Conventional Cylindrical Light Diffusers

FIG. 1 shows an example of a typical commercially available cylindricallight diffusing device 100 comprising an optical connector 10 connectingto a light source (not shown) on one end, an optical fiber 12 and acylindrical diffuser 16 on the other end. During operation, the opticalfiber 12 is in light communication with the cylindrical diffuser 16causing the cylindrical diffuser 16 to out-couple light in alongitudinally radial-symmetric irradiance distribution 18 across thelongitudinal length 19 of the cylindrical diffuser 16.

A map of the irradiance at a vertical (i.e., latitudinal) cross-section(shown as “11” in FIG. 1) through the core of the optical fiber 12 takenjust before the optical fiber 12 enters the cylindrical diffuser 16 isshown in FIG. 2. In this exemplary embodiment, the light source used isa 690 nm laser with 1 Watt launch power and this power was adjusteduntil the irradiance 18 measured at the center 17 of the longitudinallength of the diffuser 16 was 150 mW/cm². This measurement is taken 0.75mm from the central axis of the stated location of the diffuser 16. Theoptical fiber 12 from the light source leading up to the cylindricaldiffuser 16 (“lead fiber”) is 2 meters long. The optical fiber 12 has a700 μm outer diameter (“OD”) glass core and a 740 μm OD cladding. Duringoperation, the optical fiber 12 is filled with laser light having anangular distribution of a numerical aperture (“NA”) of 0.22. Thecross-section 11 was taken after 2 meter lead fiber (12). The associatedirradiance distribution graphs of FIG. 2 taken from vertical andhorizontal cross sections through the center of the map of theirradiance show that there is poor spatial uniformity of the irradiancedistribution in the core of the optical fiber 12 (“core irradiancedistribution”). The large values in the center of the graphs show thatthere is significantly higher irradiance in the center of the fiber corethan near its edges. The graph on the top of FIG. 2 shows the irradiancedistribution of the horizontal cross section while the graph on theright side of FIG. 2 shows the irradiance distribution of the verticalcross section. As shown in FIG. 2, both graphs have two axes: one axisshows width (e.g., diameter) in mm and the other axis shows irradiancein Watt/cm².

Not only does the core irradiance distribution of the optical fiber 12have poor spatial uniformity, the out-coupled longitudinallyradially-symmetric irradiance distribution along the outer surface ofirradiance emitting section of the cylindrical diffuser 16 (“diffusingirradiance distribution”) also demonstrates poor spatial uniformityleading to a non-ideal irradiance distribution as shown in FIG. 3. Thisuneven irradiance distribution is undesirable because the irradianceuniformity would not satisfy the needs of a proper “dosimetry”, meaningthe correct irradiance in light power/surface area for an optimalmedical treatment efficacy. In FIG. 3, the horizontal axis shows thelongitudinal length (in mm) used to measure the length 19 of thecylindrical diffuser 16 and the vertical axis shows the out-coupledirradiance at the surface of the cylindrical diffuser 16 measured inWatts/cm² at a distance 0.75 mm from the central axis.

FIG. 4 is an example for a typical commercially available cylindricallight diffusing device 200 comprising an optical connector 20 connectingto a light source (not shown) on one end, an optical fiber 22 and acylindrical diffuser 26 on the other end. During operation, the opticalfiber 22 is in light communication with a mode mixer 24 and thecylindrical diffuser 26 causing the cylindrical diffuser 26 toout-couple light in a longitudinally radial-symmetric irradiancedistribution 28 across the longitudinal length 29 of the cylindricaldiffuser 26.

FIG. 5 shows a map of the irradiance at a vertical cross-section (shownas “21” in FIG. 4) through the core of the optical fiber 22 taken justbefore the optical fiber 22 enters the cylindrical diffuser 26. In thisexemplary embodiment, the light source used is a 690 nm laser with 1Watt launch power and this power was adjusted until the irradiance 28measured at the center 27 of the longitudinal length of the diffuser 26was 150 mW/cm². This measurement is taken 0.75 mm from the central axisof the stated location of the diffuser 26. The optical fiber 22 from thelight source leading up to the cylindrical diffuser 26 (“lead fiber”) is2 meters long. The optical fiber 22 has a 700 μm OD glass core and a 740μm OD cladding. During operation, the optical fiber 22 is filled withlaser light having an angular distribution of a numerical aperture(“NA”) of 0.22. The cross-section 21 was taken after 2 meter lead fiber(22). Unlike FIG. 2, the associated irradiance distribution graphs shownin FIG. 5 taken from vertical and horizontal cross sections through thecenter of the map of the irradiance show that when a mode mixer (24) isused with the optical fiber 22, a “top hat” irradiance distributionprofile is achieved (i.e., variation of the irradiance distribution ofthe entire cross-section is less than +/−20% of the average irradiance),indicating a high degree of uniformity of the irradiance distribution inthe core of the fiber 22 (e.g. optimal core irradiance distribution).Similar to FIG. 2, the graph on the top of FIG. 5 shows the irradiancedistribution of the horizontal cross section while the graph on theright side of FIG. 5 shows the irradiance distribution of the verticalcross section. As shown in FIG. 5, both graphs have two axes: one axisshows width (e.g., diameter) in mm and the other axis shows irradiancein Watt/cm².

In contrast to the graph shown in FIG. 3, the out-coupled longitudinallyradially-symmetric irradiance distribution along the outer surface ofirradiance emitting section of the cylindrical diffuser 26 (e.g., thediffusing irradiance distribution) shows spatial uniformity leading toan optimal “top hat” diffusing irradiance distribution as shown in FIG.6. FIG. 6 shows that the variation of the out-coupled irradiancedistribution should be a “top hat” with less than +/−20% of the average(“I₀”) optical irradiance for a cylindrical diffuser in terms of theradially emitted irradiance distribution (e.g., optimal diffusingirradiance distribution). The horizontal axis of FIG. 6 showslongitudinal length in mm and the horizontal arrow indicates the length29 of the cylindrical diffuser 26. The vertical axis of FIG. 6 shows theout-coupled irradiance at the surface of the cylindrical diffuser 26measured in Watts/cm² at a distance 0.75 mm from the central axis.

As shown above, in order to achieve the “top hat” diffusing irradiancedistribution for a conventional cylindrical diffuser, optimal modemixing (e.g., with an effective mode mixer) in the optical fiber isrequired. The mode mixer 24 shown in FIG. 4 is created in the opticalfiber 22 by a series of five consecutive alternating tight radius bends.Another conventional mode mixing method (not shown) is to wrap theoptical fiber 22 tightly multiple times around an object (e.g. amandrel). These popular forms of mode mixing create spatial uniformityat the expense of increased transmission losses, often resulting in thelosses of 50% or more. Additionally, these techniques also create stresspoints within the optical fiber 22. Applying stress to an optical fiberis problematic because it can lead to irreversible damage to suchoptical fiber, as the micro-bending pushes the optical fiber bendingforce to the maximum fatigue limit of the glass fiber. Furthermore,these cylindrical diffuser fiber assemblies are sometimes used withoptical power that can exceed 1 Watt, which lowers the maximum fatiguelimits even more due to thermal heating from the light lost from thefiber core. This thermal heating issue can adversely impact both glassand polymer materials. Thermally destroyed mode mixers have occurred inpractice, which represents one major driver to substitute theseconventional mode mixers with an alternative according to the describedinvention.

Please note that an effective mode mixer by itself is insufficient toachieve the “top hat” diffusing irradiance distribution. An effectivelight diffuser or diffusing section is also required. For cylindricaldiffusers, the diffuser section commonly uses additional elements and/orprocessing of the diffuser section in order to achieve the “top hat”diffusing irradiance distribution. As shown in FIG. 7, one conventionalmethod is removing the cladding of the fiber tip 30 (the diffusingsection) and etching the exposed fiber core with hydrofluoric acid orgrinding it on a polishing apparatus. The resulting conical tip with itsfrosted appearance is then covered with a protective transparentenvelope 32. Referring to FIG. 8, another conventional method ismanufacturing a separate diffuser 34 containing scattering medium 36that is composed of micron-sized titanium oxide (TiO₂) particlesembedded in clear epoxy or silicone elastomer, which is encased in aprotective Teflon sheath 38. A reflector 40 attached to a plastic plug42 is then inserted into the open distal end of the sheath 38. Thepurpose of the coated plug 42 is to reflect any light that survivesforward propagation back through the scattering medium 36 where it canbe re-distributed, thus improving the uniformity of the emissionprofile. Yet another method of construction can be described as a hybridof the two previous methods wherein the cladding of an optical fiber isremoved mechanically leaving the surface of the core roughened. Thissurface is then coated with a silicone elastomer on to which a secondlayer of elastomer impregnated with titanium oxide particles isdeposited. Finally, the entire diffusing tip is encased in an outer PTFEtube which in turn is terminated with a reflective end cap in a mannersimilar to the above-described method and shown in FIG. 8. Thesedescribed techniques are costly, labor intensive and time consuming.Hence, these light diffusers are very expensive.

It should be noted there exist other conventional techniques to providea light diffuser that can produce the “top hat” diffusing irradiancedistribution such as having light scattering features on the outside ofthe optical fiber surface (e.g., divots, threads, notches, generalroughening, or the like). These techniques are labor intensive and theresulting homogeneity of the light output pattern relies strongly on aconstant fiber diameter, which can vary by up to +/−5%, making itcumbersome to achieve constant and repeatable results in themanufacturing process. Furthermore, light scattering features on thesmooth outside surface of the fiber often affect the mechanical strengthof the fiber so that for instance the tensile strength dropssubstantially.

II. Conventional Frontal Light Diffusers

Referring to FIG. 37A, an exemplary embodiment of a typical frontal(superficial) diffuser 500 is provided with 690 nm light introduced ontoan optical fiber 506 (e.g., a cylindrical optical fiber) with a 550 umdiameter core via a fiber optic connector 503. A ¼ pitch, 1 mm diametergraded index (“GRIN”) lens component 504 located at the distal endoutput face 510 of the optical fiber 506 generates the outcoupled light502. Since the desired treatment area (i.e., target) 508 has a muchlarger diameter (e.g. 42 mm) than the diameter of the optical fiber 506(e.g. 550 um), the effect of the lens component 504, to a firstapproximation, is to form an image of the output face 510 of the opticalfiber 506 onto the target 508 where the target 508 is located at somestandoff distance 512 (e.g., 64 mm) away from the lens component 504. Inthis fashion, the spatial irradiance distribution of a cross sectionalong the target 508, as shown in FIG. 37C, is closely related to thespatial irradiance distribution along a cross section of 510, as shownin FIG. 37B. Note that this exemplary embodiment exhibits low loss(e.g., −0.25 dB), where 1.0 Watt input power is enough to generate theirradiance distribution in FIG. 37C. The fiber spatial irradiancedistribution at 510 of a cylindrical fiber 506 is typically non-uniform,resulting on a non-uniform target spatial irradiance distribution at thetarget 508. This is not ideal for PIT and PDT application where aconstant, uniform spatial irradiance distribution is required over thewhole treatment area target 508.

Referring to FIG. 38A, the typical prior art addresses the issue of thenon-uniform target spatial irradiance distribution at the target 508 asshown in FIG. 37C by including a mode mixing section 520 in the fiber506 at a predetermined distanced location prior to the lens component504. The effect of the mode mixing section 520 is to convert thenon-uniform cross sectional spatial irradiance distribution at 510, asshown in FIG. 38B, to the significantly more uniform cross sectionalspatial irradiance distribution at 514, as shown in FIG. 38C. Therefore,as shown in FIG. 38D, the target spatial irradiance distribution createdby the lens component 504 at the target 508 will have a spatialirradiance distribution that is also more uniform.

The typical prior art mode mixing section 520 not only produces a moreuniform fiber spatial irradiance distribution but it also creates a moreuniform angular intensity distribution at the output of the fiber 506.However, when using a projection lens 504 to illuminate a target 508 asshown in FIG. 38A, the angular intensity distribution is not asimportant as the spatial irradiance distribution. This because the imageformed by the projection lens 504 is essentially mapping all the lightfrom one location in the fiber 506 to a location on the target 508,regardless of emission angle.

As discussed above, the mode mixing section 520 found in the prior artcan be constructed of a serpentine section of one or more tight radiusbends as shown in FIGS. 39A-39B, a coiled section of tight radius loopsas shown in FIG. 39C, or a section with multiple turns of a tight radiushelix as shown in FIG. 39D. Other art-disclosed embodiments of the modemixing section 520 may also be used (e.g., alternating sections ofgraded and step index fibers, etc.). However, all these techniquessuffer from a significant drawback, they create good mode mixing at theexpense of creating high losses in the mode mixing section 520. In oneexemplary prior art embodiment, the configuration in FIG. 38A isidentical to the configuration in FIG. 37A with the addition of a modemixing section 520 formed as shown in FIG. 39A with 7.5 mm radius bends.This embodiment exhibits a loss of −2.32 dB, requiring 3.25 Watts ofinput power to generate the irradiance distribution at the target shownin FIG. 38D.

At worst, these losses mean enough power leaks out of the fiber 506 toheat up the mode mixing section 520, resulting in catastrophic failureof the diffuser 500 and even presenting a safety concern to the operatorand the patient. More subtle drawbacks are that the losses incurred bythese types of mode mixer sections 520 tend to vary from device todevice, making it hard to produce a consistent product and making ithard to calibrate the output from the pairing of a single device with adifferent light source.

Note that the lens component 504 may be comprised of a combination ofone or more of optical elements including spherical, aspherical, gradedindex and diffractive elements. In the typical prior art, the fiber 506and lens 504 are often part of a disposable assembly and the lenscomponent 504 tends to have a small diameter.

Referring to FIG. 40A, this creates a condition where the beam of light502 emerging from the lens component 504 is diverging. The divergingnature of the typical projection lens 504 results in different beamsizes at target position locations 516, 508 and 518 located at stand-offdistance 520, 512 and 522 respectively in FIG. 40A. As the target ismoved from position 516, past 508, ending at 518, the total power in theresulting beam is the same. However, as shown in the target spatialirradiance distributions in FIG. 40B, the size of the irradiancedistribution on the target locations gets larger with distance while thevalue of the irradiance drops. This is not ideal, as the magnitude ofirradiance of the beam (power/area) drops as a function of distance fromthe output face of the lens component 504 while the area illuminatedincreases, resulting in only a narrow range of standoff values where theirradiance meets the desired treatment values.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and inventive aspects of the present invention will becomemore apparent upon reading the following detailed description, claims,and drawings, of which the following is a brief description:

FIG. 1 is a graphical depiction of a prior art exemplary cylindricallight diffusing device;

FIG. 2 is a map of the irradiance at a vertical cross-section of theoptical fiber of the cylindrical light diffusing device of FIG. 1 andits associated irradiance distribution graphs;

FIG. 3 is a graph of the out-coupled longitudinally radially-symmetricirradiance distribution of the cylindrical light diffusing device ofFIG. 1;

FIG. 4 is a graphical depiction of a prior art exemplary cylindricallight diffusing device that utilizes a mode mixer;

FIG. 5 is a map of the irradiance at a vertical cross-section of theoptical fiber of the cylindrical light diffusing device of FIG. 3 andits associated irradiance distribution graphs;

FIG. 6 is a graph of the out-coupled longitudinally radially-symmetricirradiance distribution of the cylindrical light diffusing device ofFIG. 3;

FIG. 7 is a graphical depiction of a prior art exemplary cylindricallight diffuser;

FIG. 8 is a graphical depiction of another prior art exemplarycylindrical light diffuser;

FIG. 9 is a graphical depiction of a cylindrical light diffusing deviceaccording to the present invention;

FIG. 10 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 11 is a graphical depiction of another embodiment of a cylindricallight diffusing device according to the present invention;

FIG. 12 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 13 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 14 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 15 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 16 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 17 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 18 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section;

FIG. 19 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationwith an internal scattering feature of the light diffusing section;

FIG. 20 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationwith an internal scattering feature of the light diffusing section;

FIG. 21 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationwith an internal scattering feature of the light diffusing section;

FIG. 22 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationwith internal scattering features of the light diffusing section withanother set of internal scattering feature superimposed.

FIG. 23 is a longitudinal cross-sectional view of the light diffusingsection of a non-circular core fiber exemplary embodiment accordingly tothe present invention;

FIG. 24 is a longitudinal cross-sectional view of the light diffusingsection of a non-circular core fiber exemplary embodiment accordingly tothe present invention;

FIG. 25 is a longitudinal cross-sectional view of the light diffusingsection of a non-circular core fiber exemplary embodiment accordingly tothe present invention;

FIG. 26 is a longitudinal cross-sectional view of the light diffusingsection of a non-circular core fiber exemplary embodiment accordingly tothe present invention;

FIG. 27 is a map of the irradiance at a vertical cross-section of theoptical fiber of the cylindrical light diffusing device of FIGS. 9 and14 and its associated irradiance distribution graphs;

FIG. 28 is a graph of the out-coupled longitudinally radially-symmetricirradiance distribution of the cylindrical light diffusing device ofFIGS. 9, 10, and 14;

FIG. 29 is a vertical cross-sectional view of a square shaped core fiberexemplary embodiment with the projected paths of its skew and meridionalrays;

FIG. 30 is a vertical cross-sectional view of a circular shaped corefiber exemplary embodiment with the projected paths of its skew andmeridional rays;

FIG. 31 is a graphical depiction of an exemplary cylindrical lightdiffusing device according to the present invention;

FIG. 32 is a map of the irradiance at a vertical cross-section of theoptical fiber of the cylindrical light diffusing device of FIG. 31 andits associated irradiance distribution graphs;

FIG. 33 is a vertical cross-section view of a circular shaped core fiberexemplary embodiment at a location with internal scattering features;

FIG. 34 is a graph of the out-coupled longitudinally radially-symmetricirradiance distribution of the cylindrical light diffusing device ofEXAMPLE II;

FIG. 35 is a map of the irradiance at a vertical cross-section of theoptical fiber of the cylindrical light diffusing device of FIGS. 11 and12 and its associated irradiance distribution graphs;

FIG. 36 is a graph of the out-coupled longitudinally radially-symmetricirradiance distribution of the cylindrical light diffusing device ofFIGS. 11 and 12;

FIG. 37A is a graphical depiction of a prior art exemplary frontal lightdiffusing device;

FIG. 37B is a graph of the spatial irradiance distribution along avertical cross section (510) of the optical fiber of the frontal lightdiffusing device in FIG. 37A;

FIG. 37C is a graph of the spatial irradiance distribution along avertical cross section (508) of the target by the frontal lightdiffusing device in FIG. 37A;

FIG. 38A is a graphical depiction of a prior art exemplary frontal lightdiffusing device with a mode mixing section;

FIG. 38B is a graph of the spatial irradiance distribution along avertical cross section (510) of the optical fiber of the frontal lightdiffusing device in FIG. 38A;

FIG. 38C is a graph of the spatial irradiance distribution along avertical cross section (514) of the optical fiber of the frontal lightdiffusing device in FIG. 38A;

FIG. 38D is a graph of the spatial irradiance distribution along avertical cross section (508) of the target by the frontal lightdiffusing device in FIG. 38A;

FIG. 39A is a graphical depiction of a prior art fiber optic mode mixingsection with four quarter turns with small radii;

FIG. 39B is a graphical depiction of a prior art fiber optic mode mixingsection with twelve quarter turns with small radii;

FIG. 39C is a graphical depiction of a prior art fiber optic mode mixingsection with three small radius loops formed around an axisperpendicular to the axis of the fiber;

FIG. 39D is a graphical depiction of a prior art fiber optic mode mixingsection with two helical loops formed around an axis parallel to theaxis of the fiber;

FIG. 40A is a graphical depiction of a prior art frontal light diffusingdevice shown with the targeted treatment area at various standoffdistances (520, 512, 522);

FIG. 40B is a graph of the spatial irradiance distributions alongvertical cross sections (516, 508, 518) of the targeted treatment areaat various standoff distances (520, 512, 522) by the frontal lightdiffusing device in FIG. 40A;

FIG. 41A is a graphical depiction of an exemplary embodiment of afrontal light diffusing device according to the present invention;

FIG. 41B is a graph of the spatial irradiance distribution along avertical cross section (608) of the optical fiber of the frontal lightdiffusing device in FIG. 41A;

FIG. 41C is a graph of the spatial irradiance distribution along avertical cross section (610) of the optical fiber of the frontal lightdiffusing device in FIG. 41A;

FIG. 41D is a graph of the spatial irradiance distribution along avertical cross section (614) of the target by the frontal lightdiffusing device in FIG. 41A;

FIG. 42A is a graphical depiction of another exemplary embodiment of afrontal light diffusing device according to the present invention;

FIG. 42B is a graph of the spatial irradiance distributions along avertical cross section (718) of the frontal light diffusing device ofFIG. 42A and along vertical cross sections (720, 722) of the targetedtreatment area at two standoff distances (724, 726) by the frontal lightdiffusing device in FIG. 42A; and

FIG. 43 is a vertical cross-sectional view of a non-circular core fiberexemplary embodiment accordingly to the present invention at a locationright before the diffusing proximal end of the light diffusing section.

DESCRIPTION OF THE PREFERRED EMBODIMENT

I. A Light Diffusing Device Providing a “Top Hat” Core IrradianceDistribution Without a Conventional Mode Mixer

Referring to FIGS. 9-26, the present invention provides a lightdiffusing device 300 having a non-circular core fiber 302 that providesa “top hat” core irradiance distribution (i.e., optimal core irradiancedistribution) without the necessity of using a mode mixer (e.g., 24shown in FIG. 4). The light diffusing device 300 of the presentinvention emits irradiance in a radially symmetric longitudinally “tophat” diffusing irradiance distribution (i.e., optimal diffusingirradiance distribution) without the necessity of using theabove-described known light diffusers and/or diffusing sections.

Referring to FIGS. 9 and 11, the device 300 further includes a lead-inoptical fiber 304 and at least one optical connector 306. Duringoperation, one end of the lead-in optical fiber 304 is in lightcommunication to a light source (not shown) while the other end of thelead-in optical fiber 304 is in light communication with the proximalend of the non-circular core fiber 302 through the at least one opticalconnector 306 as shown in FIGS. 9 and 11. The non-circular core fiber302 further includes a light diffusing section 308 having a diffusingproximal end 310 and a diffusing distal end 312.

In the exemplary embodiments shown in FIGS. 9 and 11, the lightdiffusing section 308 is located near the distal end of the non-circularcore fiber 302. Furthermore, the non-circular core fiber 302 mayoptionally include a light blocking means 314 (e.g., physical cap,coating such as aluminum deposition, or the like) preventing superficialor frontal light emission from the distal end of the non-circular corefiber 302. In one embodiment, the light blocking means 314 is a mirrorthat turns light around and reuses it while avoiding over illuminatingthe treatment area. It provides a highly efficient light diffusingdevice because only about 6% of the launched light couples back into thelead-in optical fiber 304.

In one embodiment, the lead-in optical fiber 304 is connected to thelight source via an additional optical connector 306. The lead-inoptical fiber 304 can be any conventional optical fiber including butnot limited to the optical fiber (12, 22) described above. The at leastone optical connector 306 connects and allows the lead-in optical fiber304 to be in light communication with the non-circular core fiber 302during operation. An alternative to the at least one optical connector306 is a conventional glue joint or fusion joint between the lead-inoptical fiber 304 and the non-circular core fiber 302. Furthermore andin an alternative exemplary embodiment, the non-circular core fiber 302actually also serves as the lead-in optical fiber 304 (resulting in asingle optical fiber) and is connected to a light source via the atleast one optical connector 306, a glue/fusion joint, or otherconventional connection means. The at least one optical connector 306can be any art-disclosed optical connector (e.g., SMA connectors or thelike).

FIGS. 13-18 each shows a vertical (i.e., latitudinal) cross-sectionalview of the non-circular core fiber 302 at location 316, which is rightbefore the diffusing proximal end 310 of the light diffusing section 308(see FIGS. 9 and 11). FIGS. 10, 12 and 19-22 each shows a verticalcross-sectional view of the diffusing distal end 312 of the lightdiffusing section 308 as shown in FIGS. 9 and 11. The non-circular corefiber 302 includes a fiber core 350. The non-circular core fiber 302 mayoptionally include a cladding 352 as shown in FIGS. 10, 12-14 and 16-18.The fiber core 350 has a non-circular geometry such as hexagon (as shownin FIGS. 10 and 12-15), square (as shown in FIGS. 16-18), rectangle,triangle, octagon, other regular polygons and non-regular polygons.Accordingly, there is a wide range of potential non-circular core shapesthat can achieve homogeneous irradiance inside the core. Some shapecharacteristics make a shape particularly well suited for the presentinvention. Although radial symmetry is not required, it does provide thebenefits of ease of manufacture and promoting radially symmetric outputirradiance pattern. The inclusion of inflection points in the crosssection profile where the tangent of the shape changes rapidlyencourages better mixing by sending adjacent rays in differentdirections. The inclusion of facets also promotes better mixing byavoiding self-focusing behavior. Avoiding re-entrant geometry aides inmanufacture and avoids physically weak structures. These shapecharacteristics combined tend to encourage the use of regular polygonshapes as the basis for the non-circular core geometry. It should alsobe noted that a core with a helical or twisted shape could also be ofinterest for generating spatially homogeneous irradiance in the core.

The cladding 352 may have the same non-circular vertical (i.e.,latitudinal) cross sectional geometry as the fiber core 350 (see e.g.,FIGS. 12, 13, and 16). Alternatively, the cladding 352 may have acircular exterior surface geometry 354 with an interior surface geometry356 that has the same general shape as the fiber core 350 (see e.g.,FIGS. 10, 14, 17 and 18).

Referring to FIGS. 15, 19-22, in some exemplary embodiments of thepresent invention, the cladding 352 does not exist but is replaced withan enclosed open cavity or environment (e.g., air) 358 between the fibercore 350 and a covering 360 that is concentric with the fiber core 350and radially envelopes (but does not tightly cladded) the fiber core350. The covering 360 can be any suitable art-disclosed polymericmaterial (e.g., Pebax®) and is generally circular in shape as shown inFIGS. 11, 12, 15, 18-22. The covering 360 offers additional protectionfor the non-circular core fiber 302. The covering 360 can be clear ortranslucent. If clear, the covering 360 does not provide any lightscattering thus no extra losses of light. If translucent, internalscattering by the covering 360 can assist in improving the uniformity ofthe diffusing irradiance distribution. However, too much internalscattering by the covering 360 can cause excess losses of light due toabsorption.

As shown in FIGS. 12 and 18, it is possible to mix and match the fibercore 350 and the cladding 352 in different vertical cross sectionalgeometries and combined them with either the enclosed open cavity 358and/or the covering 360. For example and referring to FIG. 18, avertical cross sectional view of the non-circular core fiber 302 showsits fiber core 350 has a square geometry. The interior surface geometry356 of its cladding 352 matched this square geometry while the exteriorsurface geometry 354 of its cladding 352 is circular in shape.

The non-circular core fiber 302 further includes the enclosed opencavity 358, which is sandwiched between the cladding 352 and thecovering 360. The covering 360 has a circular geometry.

In one exemplary embodiment of the device 300 and referring to FIGS. 9and 14, the fiber core 350 of the non-circular core fiber 302 isconstructed out of poly (methyl methacrylate) (“PMMA”) with a hexagonalgeometry in a circumscribed ø660 μm diameter circle. The fiber core 350is clad by the cladding 352 with an interior surface geometry 356 thathas the same hexagonal geometry as the fiber core 350. However, theexterior surface geometry 354 of the cladding 352 is circular. Thecladding 352 is constructed of a silicone with an ø740 μm OD. Thelead-in fiber 304 of the device 300 has a 200 μm OD glass core and a 230μm OD cladding. The length of the non-circular core fiber 302 is 30 cm.During operation, the core optical fiber 302 is filled with laser lighthaving an angular distribution of a NA of 0.22. It should be noted thatother embodiments could include different materials for both the coreand cladding, including utilizing various transparent or translucentglasses and polymers. If the total length of the diffuser is short, thenabsorbance in not of primary concern, but the materials should not beopaque at the wavelengths of interest. For example, if the diffuser isto be used to provide UV illumination then a silica core light guide isappropriate, whereas use of mid wave IR light would encourage the use ofa fluorite or silver halide glass. A wide range of injection moldablepolymer materials are appropriate for visible and near IR applications,including but not limited to PMMA, poly carbonate (PC) and polystyrene(PS). Various castable materials including epoxies and silicones arealso of interest. In all cases, care should be utilized to ensure thematerials could handle the required amount of optical power without illeffects, such as melting or crazing.

FIG. 27 shows a map of the irradiance at the vertical cross-section(shown as “316” in FIG. 9) through the fiber core 350 taken just beforethe diffusing proximal end 310. The light source used is a 690 nm laserwith 0.125 Watt launch power and this power was adjusted until theirradiance measured at the center 307 of the longitudinally length ofthe light diffusing section 308 was 150 mW/cm². This measurement istaken 0.75 mm from the central axis of the stated location of the lightdiffusing section 308. The total length of optical fiber (combination ofthe lead-in fiber 304 and the non-circular core fiber 302) from thelight source leading up to this location 316 is 2 meter long. Theassociated irradiance distribution graphs shown in FIG. 27 taken fromvertical and horizontal cross sections through the center of the map ofthe irradiance show the same “top hat” core irradiance distribution asthe above-discussed conventional cylindrical light diffusing device 200(shown in FIG. 5), which requires a mode mixer (24). This “top hat” coreirradiance distribution indicates a high degree of uniformity of theirradiance distribution in the fiber core 350 (i.e., optimal coreirradiance distribution). “Top hat” core irradiance distribution and/oroptimal core irradiance distribution shall be defined hereinafter inthis Specification as having all irradiance of a cross-section of thefiber core 350 to be within at least +/−20% of the average irradiance ofthe cross-section of the fiber core 350, indicating a high degree ofuniformity of the irradiance distribution in the core of the fiber 22.In some exemplary embodiments, the at least +/−20% value can be furtherreduced to +/−15% range, or even +/−10% range.

The examination of two types of rays that can propagate in a perfectlysymmetrical cylindrical light guide may assist in understanding how thenon-circular core fiber 302 of the present invention can provide a “tophat” core irradiance distribution in the fiber core 350. It is possiblefor light to propagate forward as “skew rays” that spiral around theouter edge of the fiber core 350 without ever crossing through thecenter portion of the fiber core 350. This is depicted in FIG. 30 whichshows a vertical cross-sectional view of a circular shaped core fiber301 where the projected path of a propagating skew ray 366 that alwaysstays near the edge of the fiber core 351. It is also possible to havemeridional rays 368 with paths that lie on a plane so that rays thatstart on the central axis of the light guide always cross back thoughthe central axis of the fiber core 351. In comparison and referring toFIG. 29, which shows a vertical cross-sectional view of a square shapednon-circular core fiber 302 with the projected path of similarpropagating rays. The skew ray 370 still propagates without crossing thecentral axis of the fiber core 350, but now its path is such that itsenergy can at some locations be found near the edges of the fiber core350 while in other locations it can be found closer the center of thefiber core 350. A meridional ray 372 that starts on the central axis ofthe fiber core 350 can have a path that samples much of the area of thefiber core 350 without ever crossing the axis again. These two examplesdemonstrate how introducing a large set of rays with a range ofdifferent launch angles into a non-circular core fiber 302 can yield a“top hat” core irradiance distribution after a short propagation lengththat corresponds to only a few internal reflections.

Our study indicates that replacing the non-circular core fiber 302 shownin FIG. 14 with any of the above-discussed different embodiments of thenon-circular core fiber 302 would still allow the device 300 to providethe desired “top hat” core irradiance distribution (e.g., FIGS. 13-18).For example, the fiber core 350 of FIG. 13 is same as the fiber core 350shown in FIG. 14. They both are constructed out of PMMA with a hexagonalgeometry in a circumscribed ø660 μm diameter circle. The non-circularcore fiber 302 of FIG. 13 differs from the core fiber of FIG. 14 becausethe cladding 352 of FIG. 13 has a hexagonal geometry. The cladding 352of FIG. 13 is constructed of a fluorinated polymer in a circumscribedø740 um diameter circle.

In another exemplary embodiment and referring to FIG. 15, the fiber core350 has the same geometry and dimensions as the fiber core of FIG. 14except that it is constructed out of polystyrene instead of PMMA.However, the non-circular core fiber 302 of FIG. 15 does not have thecladding 352. Instead, it (302) further includes the enclosed opencavity 358 and the covering 360. The covering 360 is constructed of atranslucent Pebax® resin with an ø1000 μm OD and an ø900 μm innerdiameter (“ID”). In this exemplary embodiment, the trapped air containedin open cavity 358 acts as a cladding to ensure the light is containedwithin the fiber core 350.

The exemplary embodiments shown in FIGS. 16-17 use the same fiber core350 constructed out of PMMA with a 500 μm×500 μm square geometry. Thenon-circular core fiber 302 of FIG. 16 has a cladding 352 constructedout of fluorinated polymer with a 540 μm×540 μm square geometry. Thenon-circular core fiber 302 of FIG. 17 has a different cladding 352 asit has a square interior surface geometry 356 and a circular exteriorsurface geometry 354. The cladding 352 is constructed of a silicone withan ø740 μm diameter OD.

In another exemplary embodiment and referring to FIG. 18, the fiber core350 has the same geometry and dimensions as the fiber core 350 of FIG.17 except that it is constructed out of polystyrene instead of PMMA.Both have the same cladding 352. However, the non-circular core fiber302 of FIG. 18 further includes the enclosed open cavity 358 and thecovering 360. The covering 360 is constructed of a translucent Pebax®resin with an ø1000 μm OD and an ø900 μm ID.

In yet another exemplary embodiment and referring to FIG. 12, thenon-circular core fiber 302 is a combination of the core fiber shown inFIG. 13 plus the enclosed open cavity 358 and the covering 360. Thecovering 360 is constructed of a translucent Pebax® resin with an ø1000μm OD and an ø900 μm ID.

As discussed above, the non-circular core fiber 302 of the presentinvention with its variety of shapes, materials, cladding (352), andcovering (360) can provide “top hat” core irradiance distributionwithout needing a mode mixer thus providing a less expensive andsturdier light diffusing device (300). The non-circular core fiber 302of the present invention can be used in conjunction with one of theabove-described conventional lighting diffusers or diffusing sections toprovide “top hat” diffusing irradiance distribution.

II. Cylindrical Light Diffusing Device Providing a “Top Hat” DiffusingIrradiance Distribution

In order for the device 300 to provide a “top hat” diffusing irradiancedistribution without using such a conventional light diffuser ordiffusing section, the device 300 must include internal (i.e., notreaching the exterior surface of the fiber core 350) scattering features362, preferably inscribed or written by laser, within the lightdiffusing section 308 as shown in FIGS. 9 and 11.

The “top hat” diffusing irradiance distribution is defined in thisSpecification as having a longitudinal variation of the out-coupledirradiance to be less than +/−20% of the average (“I₀”) opticalirradiance for a cylindrical diffuser in terms of the radially emittedirradiance distribution (see e.g., FIG. 6), indicating a high degree ofuniformity. In some exemplary embodiments, the at least +/−20% value canbe further reduced to +/−15% range, or even +/−10% range.

The internal scattering features 362 generally begin at the diffusingproximal end 310 and end at the diffusing distal end 312. The features362 can be in a variety of shapes and patterns as shown in FIGS. 10, 12,19-22. FIGS. 10, 12, 19-22 show a vertical (i.e., latitudinal)cross-sectional view of the diffusing distal end 312 of the lightdiffusing section 308. For example, the features 362 can be (i) threecylinders oriented around the central axis of the fiber core 350 at 60°increments as shown in FIGS. 10, 12 and 19 (ii) a single line of spheresconcentric to the central axis of the fiber core 350 as shown in FIG.20; (iii) a symmetrical array of elliptical features (e.g., featuresthat are elliptical or spherical) centered on radius around the centralaxis of the fiber core 350 at 60° increments as shown in FIG. 21 anddistributed down a predetermined longitudinal length of the fiber core350 in linear, nonlinear, spiral pattern, or pseudo random pattern; and(iv) a pair of parallel cylinders 361 where each cylinder of a pair arelocated at a predetermined distance from the central axis of the fibercore 350, with subsequent pairs of cylinders that are located atdifferent longitudinal locations along the length of the light diffusingsection 308 are oriented at different angles around the central axis ofthe fiber core 350, (e.g. the pair of parallel cylinders 363 are locatedat a different cross section of the fiber and are clocked at 60°relative to the pair 361). Please note that while the embodimentsdiscussed herein use 60° increments, other predetermined patterns suchmay also be suitable such as, without limitations, 45°, 72°, 90°, 120°,180° increments.

Each scattering feature 362 can be created by a suitable art-disclosedlaser. For example, a focused, mode-locked 532 nm 10 pico-second laserpulse at 1.5 Watts average power can create the features 362 shown inFIG. 10, which are comprised of three cylinders, each approximately 27μm in diameter and 270 μm in length oriented around the central axis ofthe fiber core 350 at 60° increments. In another example, a series of520 nm 400 femto-second laser pulses at 2.0 Watts average power focusedthrough an objective lens with a numerical aperture of 0.4 can createthe features 362 shown in FIG. 43 (discussed in more details below),each feature a sphere approximately 40 um in diameter centered aroundthe central axis of the fiber core 350 at increments of 60°. Please notethat while the embodiments discussed herein use 60° increments, otherdegree increments are also suitable such as 45°, 72°, 90°, 120°, 180°,etc.)

The scattering characteristics of each of the features 362 are varied bymaterial, geometry and processing. The proportion of light scattered perlength or per feature 362 must increase as the density of light perlength in the light diffusing section 308 decreases due to light beingscattered out of the non-circular core fiber 302. This can be achievedby changing the number of features 362 per unit length or the size ofthe features 362 as a function of length. Depending on the amount ofreturn light acceptable, linear increase in size may suffice but anon-linear increase in size vs length may be preferred. In anotherexemplary embodiment, the number of features 362 per unit length mayincrease while the size of the features 362 as a function of length maydecrease. It should be noted that it is also possible for one skilled inthe art to change the processing parameters in order to change theamount of scattering per feature 362.

When the internal scattering features 362 are distributed in the lightdiffusing section 308 along the central axis 364 of the non-circularfiber core 350 as shown in FIGS. 9 and 11, the light propagates down thelight diffusing section 308 and there is constant mixing occurring inthe light diffusing section 308 itself. As the light in the center ofthe fiber core 350 encounters the internal scattering features 362 andis scattered out of the light diffusing section 308, the lightredistribution ensures the irradiance in the center of the fiber core350 is replenished. This simplifies the challenge of finding a patternof scattering features 362 to achieve a uniform emission pattern whileallowing the scattering features 362 to be kept smaller and locatedtowards the center of the light diffusing section 308, resulting in apotentially more physically robust device with better emissioncharacteristics.

Referring to FIGS. 23-26, the feature 362 can also be longitudinallyspaced in a variety of patterns. For example, the features 362 can bearranged longitudinally in a uniform linear manner concentric with thecentral axis 364 of the fiber core 350 as shown in FIG. 23. The features362 can be arranged longitudinally in a non-uniform linear manner bychanging the number of the features 362 per unit length as shown in FIG.24. In FIG. 24, the number of features 362 per unit length increasesgoing from the diffusing proximal end 310 to the diffusing distal end312 of the light diffusing section 308. As discussed above and in thealternative, the number of features 362 per unit length may decreasegoing from the diffusing proximal end 310 to the diffusing distal end312 of the light diffusing section 308 but size of the features 362 mayincrease going from the diffusing proximal end 310 to the diffusingdistal end 312 of the light diffusing section 308.

Furthermore, the features 362 can be arranged longitudinally in auniform linear manner with a linear increase in size as shown in FIG.25. Finally, the features 362 can be arranged longitudinally in auniform manner with a non-linear increase in size as shown in FIG. 26.

III. Frontal Light Diffusing Device Providing a “Top Hat” SpatialIrradiance Distribution

Referring to FIG. 41A, the present invention provides a frontal lightdiffusing device 600 including a fiber optic connector 603, acylindrical optical fiber section 602, a non-circular core fiber section604, a fiber splice 605 joining the two fiber sections, and a lenscomponent 606. During the operation of the device 600, the cylindricaloptical fiber section 602 is in light communication with thenon-circular core fiber section 604, and the non-circular core fibersection 604 is also in light communication with the lens component 606.The non-circular core fiber section 604 can have the samecharacteristics as the above-discussed non-circular core fiber 302 whichprovides a “top hat” core irradiance distribution (without the necessityof using a mode mixer) except that it does not include the optionallight blocking means 314 discussed above. Please note the cross sectioncan also vary down the longitudinal length of the non-circular corefiber section 604 to assist in creating a better mixing effect, e.g.there can be one or more regions of 604 where the outer dimension of thecore increases and then decreases, or the core of 604 can have varyingamounts of twist (i.e., rotation around the longitudinal axis of thefiber section 604) instead of a straight extrusion, or the non-circularprofile of 604 can vary from one shape to another (e.g. hexagonal tosquare). The non-circular core fiber section 604 acts as a spatial modemixer to cause several internal bounces of the propagating light so thatthere is little to no loss of propagating light.

As discussed below and in one exemplary embodiment, during operation,the cylindrical optical fiber section 602 has the non-uniform fiberspatial irradiance distribution of light shown in FIG. 41B as measuredat cross section 608. The non-circular core fiber section 604 outputsthe significantly more uniform mixed fiber spatial irradiancedistribution shown FIG. 41C as measured at cross section 610. The targetspatial irradiance distribution shown in FIG. 41D created by lenscomponent 606 at the target cross section 614 is also more uniform.Accordingly, both the mixed spatial irradiance distribution measured at610 and the target spatial irradiance distribution measured at 614 havethe desired “top hat” spatial irradiance distribution. The “top hat”spatial irradiance distribution and/or optimal spatial irradiancedistribution shall hereinafter be defined as having variation of theout-coupled spatial irradiance distribution be less than +/−20% of theaverage (“I₀”) optical irradiance for a frontal diffuser in terms of theemitted irradiance distribution, indicating a high degree of uniformityof the spatial irradiance distribution at the relevant location (e.g.,at 610 and/or at target 614). In some exemplary embodiments, the atleast +/−20% value can be further reduced to +/−15% range, or even+/−10% range.

In the prior art, the mixing of propagation angles means that some raysof light that did propagate down the fiber core get perturbed intoangles that exceed the critical angle of the fiber and are emitted,resulting in transmission loss and other unwanted effects like localheating of the surrounding materials. The non-circular core fibersection 604 does not change the angles such that they cannot propagate,they only re-arrange the paths of the rays while preserving the angle ofeach ray to the optical axis of the non-circular core fiber section 604.As discussed above, it is possible to create variations in the shape orsize of the non-circular core fiber section 604 down the length of themixing section so that controlled amounts of angular mixing can beincluded in the effect of the non-circular core fiber section 604,noting that any increased angular mixing will also be accompanied byincurring corresponding transmission losses.

In one alternative embodiment of the present invention, the non-circularcore fiber section 604 can extend from the light source to theprojection lens (e.g., 606) or, as shown in FIG. 41A, a short section604 can be utilized after a cylindrical fiber section 602 and prior tothe lens component 606. Note that if a section of cylindrical fiber 602is used between the non-circular core fiber section 604 and the lenscomponent 606, care should be utilized that it not be too long (e.g.,less than 0.25 meters or the like) or the mixed spatial irradiancedistribution measured prior to 606 can become non-uniform again.

As discussed above for the non-circular core fiber 302, the non-circularcore fiber section 604 can be a separate piece of material that isconnected using standard fiber optic connectors 605 or can bepermanently affixed to one end of the cylindrical fiber section 602 byglue or even melted into place by a fusion bonding technique (e.g.,welding or the like). It is also possible to mold or emboss anon-cylindrical section 604 into an otherwise cylindrical section offiber 602. Care should be taken to engineer the junction between thecylindrical fiber section 602 and the non-circular core fiber section604 to minimized losses, e.g., matching sizes and maximum propagationangles.

Referring to FIG. 41A and in one exemplary embodiment of device 600, thecylindrical optical fiber section 602 is comprised of a core fiberconstructed out of glass with a 600 μm OD core covered by a 630 μm ODcladding. It has numerical aperture (NA)=between 0.22 and 0.26. Thenon-circular fiber core section 604 is at least 50 mm in length andconstructed out of glass with a hexagonal geometry of 600 μm ID, with a680 μm OD cladding. The lens component 606 is comprised of a ¼ pitch, 1mm diameter GRIN lens.

In one exemplary embodiment, the light source used is a 690 nm laserwith 2.4 Watt launch power and this power was adjusted until theirradiance measured at the target 614 was 150 mW/cm² with a top hatdistribution with a 42 mm internal diameter when measured with thestand-off (e.g. 616)=64 mm. This embodiment demonstrates lowtransmission losses of −0.36 dB. The total length of optical fiber(combination of the cylindrical optical fiber section 602 and thenon-circular core fiber section 604) from the light source to theprojection lens 606 is 2 meter long.

During operation, the cylindrical optical fiber section 602 has thenon-uniform fiber spatial irradiance distribution of light shown in FIG.41B as measured at cross section 608. The non-circular core fibersection 604 outputs the significantly more uniform mixed fiber spatialirradiance distribution shown FIG. 41C as measured at cross section 610.The target spatial irradiance distribution shown in FIG. 41D created bylens component 606 at the target cross section 614 is also more uniform.Accordingly, both the mixed spatial irradiance distribution measured at610 and the target spatial irradiance distribution measured at 614 havethe desired “top hat” spatial irradiance distribution.

As shown in FIG. 40A and FIG. 40B, the prior art frontal illuminatorshave diverging beams. This forces the operator to hold the illuminatorat a very specific standoff from the target zone for the duration of thetreatment in order to achieve the desired irradiance levels. An idealfrontal illuminator would have the same irradiance on the targetregardless of the standoff distance. Additionally, the ideal frontalilluminator would also allow the size and shape of the illuminationpattern on the target to easily be adjusted.

Referring to FIG. 42A, the present invention provides a frontal lightdiffusing device 700 that satisfies these goals comprising an opticalfiber 702 with a proximal connector 703, a distal termination 705, and acollimation lens assembly 704. The optical fiber 702 can be acylindrical fiber, a non-circular core fiber (e.g., 302, 604), or acombination thereof discussed above. The collimation lens assembly 704includes a collimation lens 706, which can be constructed of atransparent optical material, i.e. glass, crystal, a transparentpolymer, or a reflective material. The collimation lens 706 can becomprised of a single optical element or a combination of opticalelements. The collimation lens 706 can have any combination ofspherical, aspherical, refractive, diffractive or reflective surfacesand the materials can have a graded index profile. The naturallydivergent light output 708 of the fiber 702 is allowed to expand untilit encounters the collimation lens 706. The fiber 702 is located so itsoutput face 710 is approximately at the back focal length 712 of thecollimation lens 706. A variable aperture 714 is located near or at theoutput of the collimation lens 704 where it can block portions of thelight output 708, producing a light output beam 716 with extent thatcorresponds to the opening in 714. As shown in FIG. 42A, only thecentral portion of the light output 708 from the fiber 702 is allowedthrough the aperture 714 (i.e., collimated light output 716). Thisresulting collimated light output 716 has a “top hat” irradiancedistribution as shown in FIG. 42B that is essentially the same magnitude(e.g., less +/−20% difference in values, less than +/−15% difference invalues, or even +/−10% difference in values) in (i) the near field (e.g.cross section 720 at a standoff distance of 724), (ii) the far field(e.g. cross section 722 at a standoff distance of 726), and the distancein between the near field and the far field, hereinafter defined as“flat irradiance distribution”.

The expanding cone of rays out of the fiber 702 is deliberately allowedto overfill the collimating lens 706. The solid line in the plot in FIG.42B is the irradiance distribution measured at location 718 shown inFIG. 42A. The portions of the distribution with high variation areallowed to land on the structure of the collimation lens 704 and areblocked, reflected or absorbed. Only the uniform central portion of theirradiance distribution passes through both the collimation lens 706 andthe variable aperture 714 to generate output beam 716, resulting in theflat irradiance distribution 720, shown as a dashed line in FIG. 42B.

The aperture 714, located on the output side of the collimation lens 704blocks portions of the light output 708 that are not desired. In apreferred embodiment, the aperture 714 is an iris that allows the beamsize to be varied from 1 mm to 12 mm in diameter. Alternatively, theaperture 714 could be configured to produce a square, rectangular, oreven a non-symmetric light output.

The collimated light output 716 after the aperture 714 has very lowdivergence, so that the light output 718 is approximately the same sizein the near field, at location 720 in FIG. 42A as it is in the farfield, at location 722 in FIG. 42A. Referring to FIG. 42B, thisresulting flat irradiance distributions at cross section 720 (shown as adashed line) and cross section 722 (shown as a dash-dot line) have veryclose to flat top irradiance distribution and the beam size does notchange significantly with distance (hereinafter defined as “flatirradiance distribution”).

In one exemplary embodiment of the frontal light diffusing device 700,the input fiber has a core diameter of 400 um and a clad diameter of 430um and is filled with 1.01 Watts of 690 nm light having a numericalaperture of 0.29. The collimation lens 706 is comprised of aplano-convex lens with a 25 mm diameter and a focal length of 75 mm. Inthis embodiment, the amount of excess optical power absorbed by the handpiece when generating a 12 mm diameter beam of 150 mWatt/cm² at 720 isless than 0.85 Watts, which is easily dissipated by the body of the handpiece. Referring to FIGS. 41A-42B, the flat irradiance distribution atcross section 720 is measured at the standoff distance 724 of 100 mmfrom the aperture 714 and the flat irradiance distribution at crosssection 722 is measured at the standoff distance 726 of 200 mm from theaperture 714.

The performance of this embodiment 700 presents several advantageouscharacteristics. First, the size and geometry of the light output can beadjusted over a wide range without variation to the irradiance(mWatt/cm²) at the target. Secondly, the irradiance created on thetarget has very little dependence on the standoff distance between theprojector and the target. These features make it easy to calibrate theoutput of the light source to generate the desired levels of treatmentlight and make it easier for the operator to position the illuminator toachieve the desired exposure levels. Please note that the light outputof an unmodified cylindrical optical fiber 702 was used in FIGS. 42A. Ifan angular mode mixing section or a non-circular core fiber section(e.g., 302, 606) was used that created a more uniform, flat top angulardistribution than 718 in FIG. 42B, then a wider output beam could beobtained. Additionally, a non-circular core input fiber could be used.

EXAMPLE I

In one embodiment and referring to FIG. 31, a cylindrical lightdiffusing device 400 is provided wherein it (400) is exactly the same asthe cylindrical light diffusing device 100 discussed above except thatit (400) has the non-circular core fiber 302 instead of the conventionalcircular optical fiber 12 of the device 100. The vertical (i.e.,latitudinal) cross-sectional view of the non-circular core fiber 302 isthe same as the embodiment shown on FIG. 14. Using a 690 nm laser with 1Watt launch power as the light source and adjusting the power until theirradiance measured at the center 17 of the longitudinal length of thediffuser 16 was 150 mW/cm² resulted in the “top hat” core irradiancedistribution shown in FIG. 32. The irradiance measurement value of 150mW/cm² is measured 0.75 mm from the central axis of the stated locationof the diffuser 16. FIG. 32 shows the core irradiance distribution atthe vertical cross-section (e.g., shown as “11” in FIG. 31) through thenon-circular core fiber 302 taken just before the cylindrical diffuser16. The associated irradiance distribution graphs shown in FIG. 32 takenfrom vertical and horizontal cross sections through the center of themap of the irradiance show the same “top hat” core irradiancedistribution as the above-discussed conventional cylindrical lightdiffusing device 200, which requires a mode mixer (24). This “top hat”core irradiance distribution indicates a high degree of uniformity ofthe irradiance distribution in the fiber core 350. This demonstratesthat including a non-circular core fiber 302 prior to a cylindricaldiffuser 16 can improve the irradiance or light output characteristic ofthe device 400. However, please note that the device 400 cannot achievethe “top hat” diffusing irradiance distribution as shown in FIGS. 6, 28and 35 unless the construction of the cylindrical diffuser 16 isoptimized to account for the launch conditions. The present inventionincludes the device 400 with such optimized cylindrical diffuser 16 inorder to deliver the “top hat” diffusing irradiance distribution asshown in FIGS. 6, 28 and 36.

EXAMPLE II

In another embodiment of the present invention, a cylindrical lightdiffusing device is provided. This device has the same components as thedevice 400 discussed above in EXAMPLE I and shown in FIG. 31 except thatthe cylindrical diffuser 16 is now a conventional circular core opticalfiber having a light emitting section containing internal scatteringfeatures 362 as shown in FIG. 33. FIG. 33 shows a vertical crosssectional view of this circular core fiber's 301 light emitting sectionhaving its cladding 352 and its circular fiber core 351, which containsinternal scattering features 362. Using a 690 nm laser with 0.2 Wattlaunch power as the light source and adjusting the power until theirradiance measured at the center 17 of the longitudinal length of thecircular core fiber's light diffusing section was 150 mW/cm², thisdevice resulted in the diffusing irradiance distribution shown in FIG.34 which provides a generally “top hat” diffusing irradiancedistribution. The irradiance measurement of 150 mW/cm² is measured 0.75mm from the central axis of the stated location of the light diffusingsection. The diffusing irradiance distribution shown in FIG. 34 iscloser to the optimal “top hat” diffusing irradiance distribution shownin FIGS. 6, 28, and 36 especially when compared to the diffusingirradiance distribution of the device 100 shown in FIG. 3. For thepurpose of this specification, the term “top hat” diffusing irradiancedistribution shall include both the generally “top hat” diffusingirradiance distribution shown in FIG. 34 and the optimal “top hat”diffusing irradiance distribution shown in FIGS. 6, 28, and 36.

FIG. 34 shows that there is a potential for sub-optimal efficiency andefficacy when using internal scattering features 362 in a circular coreoptical fiber to create a light diffusing section intended to emit thedesired “top hat” diffusing irradiance distribution because as the lightpropagates forward in the light emitting section, the irradiance in theoptical axis of the optical fiber will gradually be depleted as thelight encounters subsequent scattering features and leaves the lightdiffusing section. Since there is no mode mixing within this circularcore light diffusing section, the vertical cross-sectional irradiancepattern will be less uniform, with the irradiance higher near the edgesof the fiber core and depleted near the center where the scatteringfeatures are located.

This demonstrates that it is more desirable to use a non-circular fibercore 350 than a circular fiber core for the light emission sectioncontaining the internal scattering features 362. Nevertheless, thepresent invention includes the cylindrical light diffusing devicepresented in this example and its generally “top hat” diffusingirradiance distribution because it is possible this device and itsgenerally “top hat” diffusing irradiance distribution are sufficient forcertain applications.

EXAMPLE III

In one exemplary embodiment of the device 300 and referring to FIGS. 9,10, and 14, the device 300 includes the non-circular core fiber 302, thelead-in optical fiber 304, the at least one optical connector 306.During operation, the lead-in optical fiber 304 is in lightcommunication to (i) a light source (not shown) and (ii) thenon-circular core fiber 302 via the at least one optical connector 306.The lead-in fiber 304 has a 200 μm OD glass core and a 230 μm ODcladding. The length of the non-circular core fiber 302 is 30 cm, whichdistally terminates into the light blocking means 314 made out of areflecting coating of aluminum deposition. During operation, thenon-circular core fiber 302 is filled with laser light having an angulardistribution of a NA of 0.22.

Referring FIGS. 10 and 14, the fiber core 350 of the non-circular corefiber 302 is constructed out of PMMA with a hexagonal geometry in acircumscribed ø660 μm diameter circle. The fiber core 350 is cladded bythe cladding 352 with an interior surface geometry 356 that has the samehexagonal geometry as the fiber core 350. However, the exterior surfacegeometry 354 of the cladding 352 is circular. The cladding 352 isconstructed of a silicone with a ø740 μm OD.

The non-circular core fiber 302 further includes the light diffusingsection 308 having the diffusing proximal end 310 and the diffusingdistal end 312. The light diffusing section 308 is 10.8 mm inlongitudinal length and the internal scattering features 362 begin atthe diffusing proximal end 310 and ends at the diffusing distal end 312.The features 362 are comprised of 27 sets of three cylinders. Eachcylinder is approximately 27 μm in diameter and 270 μm in lengthoriented around the central axis 364 at 60° increments as shown in FIGS.9 and 10. The 27 sets of the features 362 are arranged based upon thefollowing formula in a non-linear fashion: z_(i)=0.5i+0.0045i²−0.0003i³where the index i is an integer with values from 0 to 26 and z_(i) isthe relative z location of the i^(th) feature 362 along the axis 364.Please note that the present invention is not limited to this formula,the size of the features 362, the number of features 362 per unit lengthof the diffusing section 308, or the amount of scattering per feature362. Instead, the present invention includes other suitable spacing's,sizes, numbers of features 362 per unit length, and amounts ofscattering per feature 362.

Furthermore, the following characteristics of the device 300 may beadjusted in order to further optimize its diffusing irradiancedistribution: the longitudinal length and diameter of the diffusingsection 308, the size and geometry of the fiber core 350 and anycladding 352, the scattering characteristics of the features 362, themaximum angle coming out the of the light source and/or the lead-infiber 304, and the inclusion of the light blocking means 314 at thedistal end of the non-circular core fiber 302. This optimization can beperformed experimentally or using a ray tracing CAD program. The commonfactor in determining an optimal diffusing irradiance distribution is toengineer a linear increase in the effective scattering per incrementalvolume, as there is a linear decrease in the light density perincremental volume in the fiber core 350.

As discussed above, FIG. 27 shows a map of the irradiance at thevertical cross-section (shown as “316” in FIG. 9) through the fiber core350 taken just before the diffusing proximal end 310 for this exemplaryembodiment of the device 300. The light source used is a 690 nm laserwith 0.125 Watt launch power and this power was adjusted until theirradiance measured at the center 307 of the longitudinal length of thelight diffusing section 308 was 150 mW/cm². This measurement is taken0.75 mm from the central axis of the stated location of the lightdiffusing section 308. The total length of optical fiber (combination ofthe lead-in fiber 304 and the non-circular core fiber 302) from thelight source leading up to this location 316 is 2 meters long. Duringoperation, the non-circular core fiber 302 is filled with laser lighthaving an angular distribution of a NA of 0.22.

The associated irradiance distribution graphs shown in FIG. 27 takenfrom vertical and horizontal cross sections through the center of themap of the irradiance show the same “top hat” core irradiancedistribution as the above-discussed conventional cylindrical lightdiffusing device 200 containing a mode mixer 24. This “top hat” coreirradiance distribution indicates a high degree of uniformity of theirradiance distribution in the fiber core 350 (e.g. optimal coreirradiance distribution).

FIG. 28 shows the out-coupled longitudinally radially-symmetricirradiance distribution along the outer surface of the light diffusingsection 308 (e.g., the diffusing irradiance distribution) of thisexemplary embodiment of the device 300. The diffusing irradiancedistribution shows the optimal “top hat” irradiance distributionindicating spatial uniformity of the out-coupled longitudinallyradially-symmetric irradiance along the outer surface of the lightdiffusing section 308. The horizontal axis of FIG. 28 shows longitudinallength in mm and the horizontal arrow indicates the longitudinal lengthof the light diffusing section 308. The vertical axis of FIG. 28 showsthe out-coupled irradiance at the surface of the light diffusing section308 measured in Watts/cm² at a distance 0.75 mm from the central axis.

EXAMPLE IV

In an exemplary embodiment and referring to FIGS. 11 and 12, the device300 includes the non-circular core fiber 302, the lead-in optical fiber304, the at least one optical connector 306. During operation, thelead-in optical fiber 304 is in light communication to (i) a lightsource (not shown) and (ii) the non-circular core fiber 302 via the atleast one optical connector 306. The lead-in fiber 304 has a 200 μm ODglass core and a 230 μm OD cladding. The length of the non-circular corefiber 302 is 30 cm, which distally terminates into the light blockingmeans 314 made out of a reflecting coating of aluminum deposition.

Referring to FIG. 12, the non-circular core fiber 302 includes the fibercore 350 constructed out of PMMA with a hexagonal geometry in acircumscribed ø660 μm diameter circle. The fiber core 350 is cladded bythe cladding 352 with an interior surface geometry 356 that is samehexagonal geometry as the fiber core 350. However, the exterior surfacegeometry 354 of the cladding 352 is circular. The cladding 352 isconstructed of a polymer with a ø740 μm OD. The non-circular core fiber302 further includes the enclosed open cavity 358 and the covering 360.The covering 360 is constructed of a translucent Pebax® resin with aø1000 μm OD and a ø900 μm ID. The covering is heat sealed at one or bothof its ends.

The non-circular core fiber 302 further includes the light diffusingsection 308 having the diffusing proximal end 310 and the diffusingdistal end 312. The light diffusing section 308 is exactly the same asthe light diffusing section 308 of the embodiment described above inExample III including its internal scattering features 362.

FIG. 35 shows a map of the irradiance at the vertical cross-section(shown as “316” in FIG. 11) through the fiber core 350 taken just beforethe diffusing proximal end 310 for this exemplary embodiment of thedevice 300. The light source used is a 690 nm laser with 0.125 Wattlaunch power and this power was adjusted until the irradiance measureduntil the irradiance measured at the center 307 of the longitudinallength of the light diffusing section 308 was 150 mW/cm². Thismeasurement is taken 0.75 mm from the central axis of the statedlocation of the light diffusion section 308. The total length of opticalfiber (combination of the lead-in fiber 304 and the non-circular corefiber 302) from the light source leading up to this location 316 is 2meters long. During operation, the non-circular core fiber 302 is filledwith laser light having an angular distribution of a NA of 0.22.

The associated irradiance distribution graphs shown in FIG. 35 takenfrom vertical and horizontal cross sections through the center of themap of the irradiance show the same “top hat” core irradiancedistribution as the above-discussed conventional cylindrical lightdiffusing device 200 with a mode mixer (24). This “top hat” coreirradiance distribution indicates a high degree of uniformity of theirradiance distribution in the fiber core 350.

FIG. 36 shows the out-coupled longitudinally radially-symmetricirradiance distribution along the outer surface of the light diffusingsection 308 (e.g., the diffusing irradiance distribution) of thisexemplary embodiment of the device 300. The diffusing irradiancedistribution shows the optimal “top hat” irradiance distributionindicating spatial uniformity of the out-coupled longitudinallyradially-symmetric irradiance along the outer surface of the lightdiffusing section 308. The horizontal axis of FIG. 36 shows longitudinallength in mm and the horizontal arrow indicates the longitudinal lengthof the light diffusing section 308. The vertical axis of FIG. 36 showsthe out-coupled irradiance at the surface of the light diffusing section308 measured in Watts/cm² at a distance 0.75 mm from the central axis.

EXAMPLE V

In an exemplary embodiment and referring to FIGS. 11 and 43, the device300 includes the non-circular core fiber 302, the lead-in optical fiber304, the at least one optical connector 306. During operation, thelead-in optical fiber 304 is in light communication to (i) a lightsource (not shown) and (ii) the non-circular core fiber 302 via the atleast one optical connector 306. The lead-in fiber 304 has a 200 μm ODglass core and a 230 μm OD cladding. The length of the non-circular corefiber 302 is 30 cm, which distally terminates into the light blockingmeans 314 made out of a reflecting coating of aluminum deposition.

Referring to FIG. 43, the non-circular core fiber 302 includes the fibercore 350 constructed out of glass with a hexagonal geometry in acircumscribed ø460 μm diameter circle. The fiber core 350 is cladded bythe cladding 352 with an interior surface geometry 356 that is samehexagonal geometry as the fiber core 350. However, the exterior surfacegeometry 354 of the cladding 352 is circular. The cladding 352 isconstructed of a glass with a ø480 μm OD. The non-circular core fiber302 further includes the enclosed open cavity 358 and the covering 360.The covering 360 is constructed of a translucent Pebax® resin with aø1000 μm OD and a ø800 μm ID. The covering is heat sealed at one or bothof its ends.

The non-circular core fiber 302 further includes the light diffusingsection 308 having the diffusing proximal end 310 and the diffusingdistal end 312. The light diffusing section 308 is 11.3 mm inlongitudinal length and the internal scattering features 362 begin atthe diffusing proximal end 310 and ends at the diffusing distal end 312.The features 362 are comprised of 37 sets of 6 ellipses. Each ellipse isapproximately spherical with a 40 μm diameter and is located 100 um fromthe central axis of the fiber core 350 and distributed at 60°incrementsas shown in FIG. 43. The 37 sets of the features 362 are arranged basedupon the following formula in a non-linear fashion:z_(i)=0.35i+0.00015i²−0.000032i³ where the index i is an integer withvalues from 0 to 36 and z_(i) is the relative z location of the i^(th)feature 362 along the axis 364. Please note that the present inventionis not limited to this formula, the size of the features 362, the numberof features 362 per unit length of the diffusing section 308, or theamount of scattering per feature 362. Instead, the present inventionincludes other suitable spacing's, sizes, numbers of features 362 perunit length, and amounts of scattering per feature 362.

The light source and the total length are exactly the same as theembodiment described above in Example IV and the map of the irradianceat the vertical cross-section 316 has values that are within +/−10% tothat shown in FIG. 35. When the source is adjusted in the same fashionas in Example IV, the diffusing irradiance distribution shows an optimal“top hat” irradiance distribution that has values that are within +/−20%as shown in FIG. 36.

EXAMPLE VI

In an exemplary embodiment and referring to FIG. 41A, the presentinvention provides a frontal light diffusing device 600 includes a fiberoptic connector 603, a cylindrical fiber section 602, a non-circularcore fiber 604, a pair of optical connectors 605, and a lens component606. During operation, the cylindrical fiber section 602 is in lightcommunication to (i) a light source (not shown) via fiber opticconnector 603 and (ii) the non-circular core fiber section 604 is alsoin light communication with the lens component 606.

The fiber optic connector 603 is SMA style and the cylindrical fibersection 602 has a 200 μm OD glass core and a 220 μm OD cladding and a700 um OD Tefzel jacket. The pair of fiber optical connectors 605 areSMA style and the non-circular core fiber 604 has a hexagonal glass corewith a circumscribed 460 um diameter and a cylindrical glass core with a480 um external diameter and is covered by a 1.05 mm diameter Tefzeljacket. The lens component 606 is a 0.5 NA, ¼ pitch GRIN lens with a 0.8mm OD that is affixed to the distal end of the non-circular core fiber604 with an optical epoxy. The length of the non-circular core fiber is30 cm and the combined length of the frontal light diffusing device 600is 2 meters.

The light source used is a 690 nm laser that couples 2.2 Watts of 0.22NA launch power into the lead in fiber 602 and this power is adjusteduntil the irradiance measured at the target 614 with a stand-off 616 of80 mm is 150 mW/cm² with a top hat distribution with a 40 mm internaldiameter that has values that are within +/−10% of the FIG. 41D.

Please note that unless otherwise expressly stated, all diffusingirradiance distribution data presented in this specification anddrawings (e.g., FIGS. 2-3, 5-6, 27-28, 34-36) are taken 0.75 mm from thecentral axis of the applicable location of either the fiber core or thediffuser.

The method of the present invention further includes applying aphotosensitive drug composition to desired treatment site; placing thedevice (300, 400) described interstitially inside the desired treatmentsite and applying light delivered by the device 300 to the treatmentsite at a wavelength absorbed by the photosensitive drug composition soas to inhibit targeted cells located within the treatment site.

Although there has been hereinabove described a fiber optic lightdiffusing device and method for PIT, PDT and other light activatedtherapies in accordance with the present invention, for purposes ofillustrating the manner in which the invention may be used to advantage,it will be appreciated that the invention is not limited thereto.Accordingly, any and all modifications, variations, or equivalentarrangements which may occur to those skilled in the art should beconsidered to be within the scope of the present invention as defined inthe appended claims.

What is claimed is:
 1. A cylindrical light diffusing device comprising a non-circular core fiber having: i) a non-circular fiber core that provides a “top hat” core irradiance distribution; ii) light blocking means that prevent frontal light emission from distal end of the non-circular core fiber and return the frontal light back into the non-circular core fiber for redistribution and emission by a light diffusing section; and iii) the light diffusing section having a diffusing proximal end, a diffusing distal end, and internal scattering features distributed within the non-circular fiber core of the light diffusing section along central axis of the fiber core, wherein interactions among the non-circular fiber core, the light blocking means, and the internal scattering features allow the light diffusion section to (a) provide for a constant mixing of light within the light diffusion section resulting in a redistribution of the light that ensures irradiance in center of the fiber core is replenished; and (b) emits irradiance in a radially symmetric longitudinally “top hat” diffusing irradiance distribution.
 2. The light diffusing device of claim 1 wherein the internal scattering features are three cylinders oriented around the central, axis of the fiber core of the light diffusing section of the fiber core at 60° increments.
 3. The light diffusing device of claim 1 wherein the internal scattering features are a single line of spheres concentric to the central axis of the fiber core of the light diffusing section.
 4. The light diffusing device of claim 1 wherein the internal scattering features are a symmetrical array of elliptical features centered on a radius around the central axis of the fiber core at a predetermined pattern and distributed down a predetermined longitudinal length of the fiber core of the light diffusion section in a pattern selected from the group consisted of linear, nonlinear, spiral, and pseudo random.
 5. The light diffusing device of claim 4 wherein the predetermined pattern is at 60° increments.
 6. A cylindrical light diffusing device comprising a non-circular core fiber having: i) a fiber core that provides a “top hat” core irradiance distribution; ii) light blocking means that prevent frontal light emission from distal end of the non-circular core fiber; and iii) a light diffusing section having a diffusing proximal end, a diffusing distal end, and internal scattering features distributed within the non-circular fiber core of the light diffusing section along central axis of the fiber core, wherein: a) the light diffusion section emits irradiance in a radially symmetric longitudinally “top hat” diffusing irradiance distribution; b) the internal scattering features are pairs of parallel cylinders located at different longitudinal locations along the fiber core of the light diffusing section; wherein (i) each cylinder within each pair of the parallel cylinders is located at a predetermined distance from the central axis of the fiber core of the light diffusing section; and (ii) each pair of the parallel cylinders is oriented at different angles around the central axis than an adjacent pair of the parallel cylinders.
 7. The light diffusing device of claim 1 wherein the internal scattering features are created by a laser.
 8. The light diffusing device of claim 1 wherein the internal scattering features are located longitudinally in a uniform linear manner concentric with the central axis of the fiber core of the light diffusing section.
 9. The light diffusing device of claim 1 wherein pattern of the internal scattering features are located longitudinally in a non-uniform linear manner concentric with the central axis of the fiber core of the light diffusing section and number of internal scattering features per unit length increases from the diffusing proximal end to the diffusing distal end.
 10. The light diffusing device of claim 1 wherein size of each of the internal scattering features increases from the diffusing proximal end to the diffusing distal end.
 11. The light diffusing device of claim 1 wherein size of each of the internal scattering features decreases from the diffusing proximal end to the diffusing distal end.
 12. The light diffusing, device of claim 1 wherein the “top hat” diffusing irradiance distribution means that longitudinal variation of radially emitted irradiance from the light diffusing section is less than +/−20% of the average (“I₀”) optical irradiance.
 13. The light diffusing device of claim 1 wherein the “top hat” diffusing irradiance distribution means that longitudinal variation of radially emitted irradiance from the light diffusing section is less than +/−15% of the average (“I₀”) optical irradiance.
 14. The light diffusing device of claim 1 wherein the “top hat” diffusing irradiance distribution means that longitudinal variation of radially emitted irradiance from the light diffusing section is less than +/−10% of the average (“I₀”) optical irradiance.
 15. A cylindrical light diffusing device comprising a non-circular core fiber having: i) a non-circular fiber core that provides a “top hat” core irradiance distribution; ii) light blocking means that prevent frontal light emission from distal end of the non-circular core fiber and return the frontal light back into the non-circular core fiber for redistribution and emission by a light diffusing section; and iii) the light diffusing section having a diffusing proximal end, a diffusing distal end, and internal scattering features distributed within the non-circular fiber core of the light diffusing section along central axis of the fiber core, wherein interactions among the non-circular fiber core, the light blocking means, and the internal scattering features allow the light diffusion section to provide a constant mixing of light within the light diffusion section resulting in a redistribution of the light that ensures irradiance in center of the fiber core is replenished; and (b) a “top hat” diffusing irradiance distribution, thereby limiting variation of radially emitted irradiance longitudinally from the light diffusing section to be within +/−15% of the average (“I₀”) optical irradiance.
 16. The light diffusing device of claim 1 wherein latitudinal, cross sectional shape of the non-circular fiber core is selected from the group consisting of hexagon, square, rectangle, triangle, octagon, other regular polygons, and non-regular polygons.
 17. The light diffusing device of claim 1 wherein the non-circular core fiber further comprises a covering, a cladding, and an enclosed open cavity located between, and created by, the covering and the cladding; wherein the cladding encloses the core fiber.
 18. The light diffusing device of claim 17 wherein the cladding has an exterior, latitudinal, cross sectional shape that is different from the cladding's interior, latitudinal, cross sectional shape.
 19. The diffusing device of claim 18 wherein the exterior, latitudinal, cross sectional shape of the cladding is circular; and the interior, latitudinal, cross sectional shape of the cladding is same as the latitudinal, cross sectional shape of the fiber core.
 20. The diffusing device of claim 1 wherein the light blocking means is a mirror.
 21. A cylindrical light diffusing device comprising a non-circular core fiber having: i) a non-circular fiber core that provides a “top hat” core irradiance distribution; ii) light blocking means that prevent frontal light emission from distal end of the non-circular core fiber and return the frontal light back into the non-circular core fiber for redistribution and emission by a light diffusing section; iii) the light diffusing section having a diffusing proximal end, a diffusing distal end, and internal scattering features distributed within the non-circular fiber core of the light diffusing section are located longitudinally in a non-uniform spiral manner concentric with central axis of the non-circular fiber core of the light diffusing section, wherein interactions among the non-circular fiber core, the light blocking means, and internal scattering features allow the light diffusion section to (a) provide for a constant mixing of light within the light diffusion section resulting in a redistribution of the light that ensures irradiance in center of the fiber core is replenished; and (b) emit irradiance in a radially symmetric longitudinally “top hat” diffusing irradiance distribution; and iv) a translucent covering over the light diffusion section. 